OBJECTIVES: 1) The human variation in galactose-1-phosphate uridylyltransferase will continue to be studied. Using an immuno-absorbent column, normal and variant enzymes will be isolated and the purified proteins characterized both biochemically and immunologically. Isotopically labeled enzyme will also be purified from cells cultured from normal and mutant individuals. 2) Statistical methodology for analyzing the distribution of quantitative activity of galactose enzymes will be extended to develop more general approaches to the dissection of continuous distributions from the standpoint of identifying the frequency of mutant alleles. 3) Variation at the Glk locus in the mouse which has been found to be responsible for variations in whole blood as well as liver galactokinase activity will be analyzed both genetically and biochemically.